PQ G-P01[ ].qxd 1/24/04 9:10 AM Page 1 Quark03 Quark03:Desktop Folder:REPRO-miller. Power Hacksaws, Power Band Saws, and Circular Saws

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1 PQ G-P01[ ].qxd 1/24/04 9:10 AM Page 1 Quark03 Quark03:Desktop Folder:REPRO-miller Chapter 1 Power Hacksaws, Power Band Saws, and Circular Saws Power hacksaws, power band saws, and circular saws are very important to machine shop operations. A large number of power hacksaws and power band saws are in use in the metalworking industry. Power Hacksaws A power hacksaw is an essential machine in most machine shop operations. For many years a hand-operated hacksaw was the only means for sawing off metal. Power-driven machines for driving metal-cutting saw blades have been developed to make the task easier. The power hacksaw can do the work much more rapidly and accurately. The machinist should be familiar with these machines, the blades used on the machines, and the operations performed on them. One type of power hacksaw commonly found in machine shops is shown in Figure 1-1. Figure 1-1 Power hacksaw. Basic Construction Power hacksaws are designed to make the sawing of metal a mechanical operation. The stock is usually held in a vise mounted on the base of the machine. An electric motor is used to supply power for the machine. 1

2 PQ G-P01[ ].qxd 1/24/04 9:10 AM Page 2 Quark03 Quark03:Desktop Folder:REPRO-miller 2 Chapter 1 Drive Mechanism The drive shaft is connected by a V-belt and gears to the electric motor mounted on the machine. The drive mechanism is shielded by guards for safety in operation. Frame A U-shaped frame is used on the smaller power hacksaws to support the two ends of the saw blade, which is under tension. The heavier machines use a four-sided frame and a thin backing plate for the blade of the saw. Worktable and Vise Most worktables are equipped with a vise that can be mounted either straight or angular to the blade. The worktable is usually mounted on a ruggedly constructed base. Many worktables are provided with T-slots for the purpose of supporting special clamping devices. Special Features Nearly all power hacksaws raise the blade on the return stroke. This feature prevents dulling of the blade by dragging it over the work as the blade is returned to the starting position. Another important feature is a blade safety switch that automatically stops the machine if the blade should break during operation of the saw. The safety switch prevents any damage that could result if the machine continued operation with a broken blade. Coolant System Some power hacksaws are equipped with a coolant system that delivers a coolant to the hacksaw blade. The coolant passes from a receiving tank to a pump and then to the work. The machine is equipped with a trough to catch the coolant, which may be screened to remove any chips of metal. Saw Capacity Small power hacksaws can be used on square or round stock ranging from 1 8 inch to 3 inches. The larger machines have a capacity ranging to 12 inches (square or round), or even larger. The capacity of a machine for angular cuts is different from its capacity for straight cuts. The cutting surface is longer for angular cutting. Thus, the saw must be equipped not only with a swivel vise but also with a long enough stroke to make the angular cut. Blades High-speed tungsten steel and high-speed molybdenum steel are the most commonly used materials in power saw blades. If only the teeth are hardened, the blades are called flexible blades.

3 PQ G-P01[ ].qxd 1/24/04 9:10 AM Page 3 Quark03 Quark03:Desktop Folder:REPRO-miller Power Hacksaws, Power Band Saws, and Circular Saws 3 Power hacksaw blades are ordered by specifying length and width, thickness, and teeth per inch. For example, they are available in 12 1 length and width at inch thickness. The teeth per inch (TPI) would be either 10 or 14. The blade is available in only 14 TPI. Blades also come in 17 1 with a thickness of inch and either 10 or 14 TPI. Blades with a thickness of 62 thousandths of an inch (0.062 inch) are usually inches wide. High-speed, shatterproof blades are designed to meet safety and performance requirements. The high-speed molybdenum blades are longer wearing and give the best results for general use. They, too, come in 12-inch, 14-inch, and 17-inch lengths with a 1-inch or inch width. These blades are made in both 10 and 14 TPI sizes. Thickness of the metal being cut determines the number of teeth per inch chosen to do the job. There should be no fewer than two or three teeth touching the metal being cut. Figure 1-2 shows the power hacksaw blade end with a hole for mounting in the machine and the pointed nature of the teeth. Figure 1-2 blade. Power hacksaw Hacksaw Operation Straight cuts are made easily on power hacksaws. The vise is stationary, and the cut is made at a right angle to the sides of the stock. Most machines are equipped with an adjustable vise. Angular cuts at any desired angle up to 45 degrees can be made by swiveling the vise. To operate the power saw properly, the work should be fastened securely in the vise so that the blade will saw in the proper place. The blade will break if the work loosens in the vise. The saw blade should be lowered onto the work carefully to start the cut. On some machines this is done by hand, but it can be done automatically on some saws. In either method, the points of the teeth will be broken or damaged if the blade is permitted to strike the work suddenly. The machine should be watched carefully to make certain that the saw blade lifts about 1 8 inch on the return stroke. If the blade

4 PQ G-P01[ ].qxd 1/24/04 9:10 AM Page 4 Quark03 Quark03:Desktop Folder:REPRO-miller 4 Chapter 1 fails to lift, adjustments should be made immediately, as the blade will be damaged if operation is continued. When making angular cuts with the work turned at an angle in the vise, another precaution is to be certain that the saw blade can make both the backward and the forward strokes without the saw frame making contact with either the work or the vise. Serious damage to the machine can result from failure to observe this precaution. When a saw blade is replaced, or a new blade is started in an old cut, it should be remembered that the set of the new blade is wider. The new blade will stick in the old cut unless the work is rotated in the vise a quarter turn. If the work cannot be rotated, the new blade should be guided into the old cut. The cutting speed of a power hacksaw, of course, varies with the material being cut. Suggested cutting speeds are as follows: for mild steel, 130; for tool steel (annealed), 90; and for tool steel (unannealed), 60. For example, on a machine with a 6-inch stroke, the revolutions per minute of the driving crank should be 130. All steels should be cut with a cutting compound. Bronze should be cut with a suitable compound at the same speed as mild steel. The saw blade will heat rapidly if an attempt is made to cut brass without a cutting compound adapted to brass. Brass may be cut at the same speed as steel if a suitable compound is used. Power Band Saws In the past few years the power band saw has become very important in machine shop operations. In some instances it is used in production operations prior to final machining operations. Basic Construction Power band saws are also designed to make the sawing of metal a mechanical operation (Figure 1-3). The stock can be held in a vise mounted on the machine or it can be supported by the operator s hand. Electric motors are used to supply the power for the band saws. Drive Mechanism Wheels on the power band saw can be adjusted to apply tension to the band saw blade, which is a flexible, thin, narrow ribbon of steel. One of these wheels is powered by the electric motor mounted on the machine. These wheels are enclosed by guards for safety in operation. Frame Many variations of power band saws are available. However, band saws can be grouped into three classifications: horizontal machines for cut-off sawing, vertical machines for straight and profile sawing

5 PQ G-P01[ ].qxd 1/24/04 9:10 AM Page 5 Quark03 Quark03:Desktop Folder:REPRO-miller Power Hacksaws, Power Band Saws, and Circular Saws 5 Figure 1-3 A power band saw. (Courtesy Kalamazoo Saw Div., KTS Industries.) at conventional speeds, and vertical machines for nonferrous cutting and friction cutting. Worktable and Vise Power band saws have either a worktable or vise to hold the metal that is to be cut. The worktable is usually part of the band saw. The vise, if there is one, is usually designed to fit the worktable. Many worktables also have T-slots for the purpose of supporting special clamping devices to hold the work to be cut. Special Features Some power band saws have automatic tensioning devices so that the proper amount of tension is applied to the band saw at all times. This type of device reduces excessive wear and damage to the blade. Coolant System Coolant systems are common on power band saws designed for high-speed production work. These systems deliver coolant to the

6 PQ G-P01[ ].qxd 1/24/04 9:10 AM Page 6 Quark03 Quark03:Desktop Folder:REPRO-miller 6 Chapter 1 band saw blade and the work. After the coolant has been used, it is recycled through a screen and filter to remove any chips. Capacity of Power Band Saws The maximum capacity of power band saws varies according to the size of the band saw. Some of the larger machines can accommodate work that is and larger. Band saws also have the capacity to do a wide variety of operations that include cut-off, straight sawing, and contour, or profile, sawing. Rough shaping and semifinishing can be accomplished on almost all types of ferrous and nonferrous materials. Blades The development of the heavy-duty band saw machine tool has been designed and built to operate with high-speed blades at maximum efficiency. Use of the band saw offers several important advantages over the hacksaw. These advantages include a narrower kerf, which results in greatly reduced losses; fast, efficient cutting with low per-cut costs; and consistently smooth, accurate cutting. The type of blade used on the power band saw is very important. Blades are available with many different types of teeth, tooth set, and pitch. The three types of teeth are the regular tooth, skip tooth, and hook tooth (Figure 1-4). The regular tooth blade provides from 3 to 32 teeth per square inch. Teeth may be raker set Figure 1-4 Three tooth styles for blades. or wavy set. Regular tooth blades are preferred for all ferrous metals and for general-purpose cutting. Skip-tooth blades feature widely spaced teeth (usually from 2 to 6 TPI) to provide the added chip clearance needed for cutting softer materials. Teeth of the skip-tooth blade are characterized by straight 90 faces and by the sharp angles at the junction of the tooth and gullet. Since these sharp angles and flat surfaces tend to break up chips, this type of tooth is preferred for the very soft nonferrous metals that would otherwise tend to clog and gum the blade. This blade is also widely used in woodcutting. Hook-tooth blades provide the same wide tooth spacing as the skip-tooth blade. The teeth themselves have a 10 undercut face. Gullets are deeper with blended radii between the teeth and the

7 PQ G-P01[ ].qxd 1/24/04 9:10 AM Page 7 Quark03 Quark03:Desktop Folder:REPRO-miller Power Hacksaws, Power Band Saws, and Circular Saws 7 gullets. Since the undercut face helps the teeth dig in and take a good cut, the blended radii tend to curl the chips. This type of tooth is preferred for the harder nonferrous alloys and many plastic operations. There are three basic types of tooth set on metal-cutting band saw blades. Each tooth set is designed for a specific type of cutting application. These three basic types of tooth sets are the raker set, the wavy set, and the alternate set. See Figure 1-5. Figure 1-5 Types of tooth sets for blades. The raker set one tooth set left, one tooth set right, and one tooth not set is preferred for all long cutting runs where the type of material and the size and shape of the work remain relatively constant. It is also for all contour, or profile, cutting applications and for band sawing with high-speed steel blades. The wavy-set blade, a rolled set with alternate left and right waves, provides greater chip clearance and a stronger, nearly ripproof tooth. This blade is preferred for general-purpose work on conventional horizontal machines. The alternate set has every tooth set one to the left, one to the right throughout the blade. Taken originally from the carpenter handsaw, it was supplied in band saws for brass foundry applications. Band Saw Operation When operating a band saw, there are some general principles that should be followed so that you will be able to select the blade with the proper pitch: Small and thin-wall sections of metal require fine teeth. Large metal sections require the use of blades with coarse teeth so that adequate chip clearance is provided.

8 PQ G-P01[ ].qxd 1/24/04 9:10 AM Page 8 Quark03 Quark03:Desktop Folder:REPRO-miller 8 Chapter 1 Two teeth should be engaged in the metal to be cut at all times. Soft, easily machined metals require slightly coarser teeth to provide chip clearance. Hard metals of low machinability require finer teeth so that there are more cutting edges per inch. Stainless steel should be sawed with a coarse (NQ) tooth saw blade for best results. Figure 1-6 shows tooth pitches. Figure 1-6 Tooth pitches. Select the widest blade that your machine will accommodate when straight, accurate cutting is required. Blade widths for contour sawing depend upon the specific application. Profile (or contour) sawing is an accurate, fast, and efficient method of producing complex contours in almost any machinable metal. With the proper blade selection, radii as small as 1 16 inch can be cut. Either internal or external contours can be sawed. If an internal contour has to be sawed, it is first necessary to drill a hole within the contour area to accommodate the saw blade. The band saw blade has to be cut to length, threaded through the drilled hole, and then rewelded. It is for this reason that band saws designed and built for contour sawing have a built-in butt welder. Blades for profile sawing are always raker set because this type of tooth provides

9 PQ G-P01[ ].qxd 1/24/04 9:10 AM Page 9 Quark03 Quark03:Desktop Folder:REPRO-miller Power Hacksaws, Power Band Saws, and Circular Saws 9 Figure 1-7 Bandwidth selection for profile or contour sawing. the necessary side clearance. These blades are usually narrower than those chosen for straight cutting; the extra width for any specific job depends upon the smallest radius to be cut. Figure 1-7 will aid you in selecting the correct blade for any application. Profile sawing requires cutting and rewelding the blade. Because of this, it is necessary to make a good weld. This can be accomplished very easily if certain steps are followed. The steps are as follows: 1. Square both ends of the blade accurately. 2. Align both ends of the blade so that they join evenly across the entire width of the blade. 3. Select the correct dial setting for the blade width. 4. Select the correct annealing period. 5. Dress the blade to remove the welding flash. 6. Anneal for stress relieving. With the exception of cast iron, coolant should be used for all band-sawing operations. Cast iron is always cut dry. Almost all of the commercially available soluble oils or light cutting oils will give good results when cutting ferrous metals. When aluminum is cut, paraffin and beeswax are commonly used lubricants.

10 PQ G-P01[ ].qxd 1/24/04 9:10 AM Page 10 Quark03 Quark03:Desktop Folder:REPRO-mille 10 Chapter 1 The recommendations shown in Table 1-1 are based on four types of cutting fluids: A. Cutting oil mineral base with fatty oils added (has sulfur for antiweld characteristics and chlorine for film strength) B. Cutting oil with light viscosity fatty oils (for cold-weather operations, mix with (A); when cutting copper alloys, additives and chlorine should be added) C. Synthetic water-soluble cutting agent D. Soluble oil cutting agent with fatty oils (sulfurized for extreme pressure with antiweldment properties; water-soluble for greater heat removal) Table 1-1 Recommended Cutting Fluids Materials to Be Cut Cutting Fluids Recommended Aluminum Stainless Alloys; Free-Cutting Alloy Steels Leaded Steels; Steels; (Free Stainless Brass; Brass; Carbon Nickel Cutting); (Austenitic); Magnesium Gun Steels; Cast Steel; Ingot Manganese Alloys; Metal; Steels; Nickel- Iron; Steels; Phosphor Nickel; Malleable Chromium Wrought High-Temp Bronze; Monel; Operation Iron Steel Iron Alloys Zinc Inconel Production FLOOD FLOOD FLOOD FLOOD FLOOD FLOOD sawing using MARVEL high-speed steel, highspeed-edge, and intermediate alloy steel band blades (B) (A) (A) (A) (B) (A) (C) Mix 1 (C) Mix 1 (D) Mix (C) Mix 1 (C) Mix to 5 with to 5 with 1 to 5 to 5 with 1 to 5 water. water. with water. with water. water. (D) Mix 1 (D) Mix 1 (C) Mix (D) Mix 1 (D) Mix to 5 with to 5 with 1 to 5 to 5 with 1 to 5 water. water. with water. with water. water.

11 PQ G-P01[ ].qxd 1/24/04 9:10 AM Page 11 Quark03 Quark03:Desktop Folder:REPRO-mille Power Hacksaws, Power Band Saws, and Circular Saws 11 Table 1-1 (continued) Materials to Be Cut Cutting Fluids Recommended Aluminum Stainless Alloys; Free-Cutting Alloy Steels Leaded Steels; Steels; (Free Stainless Brass; Brass; Carbon Nickel Cutting); (Austenitic); Magnesium Gun Steels; Cast Steel; Ingot Manganese Alloys; Metal; Steels; Nickel- Iron; Steels; Phosphor Nickel; Malleable Chromium Wrought High-Temp Bronze; Monel; Operation Iron Steel Iron Alloys Zinc Inconel General DRIP (blade DRIP DRIP DRIP DRIP DRIP sawing just wet) (blade (blade (blade (blade (blade using just wet) just wet) just wet) just wet) just MARVEL wet) hard-back & flexibleback hardenededge band blades (B) (B) (B) (A) (B) (A) (D) (D) (D) (B) Paraffin (B) dry Contour SPRAY OR SPRAY SPRAY FLOOD FLOOD sawing DRIP OR OR OR using DRIP DRIP DRIP MARVEL high-speededge or hard-back & flexibleback carbon blades (C) (C) (C) (D) Mix 1 (B) (B) to 10 with water. (D) Mix 1 (D) Mix 1 (D) Mix (C) Mix 1 Paraffin (A) to 10 with to 10 1 to 10 to 10 with dry water. with with water. water water. (B) (A) Courtesy Armstrong-Blum Mfg. Co.

12 PQ G-P01[ ].qxd 1/24/04 9:10 AM Page 12 Quark03 Quark03:Desktop Folder:REPRO-mille 12 Chapter 1 The three types of feeds used on power band saws are hand, hydraulic, and mechanical. The number of factors involved in the efficient and trouble-free operation of a power band saw make it difficult to provide specific information on the proper speed or pressure required (see Table 1-2). When a cut is started, the blade should not be forced. If the work is forced into the blade, it will result in a shorter blade life and defective work. The following principles should be used as a guide in selecting the proper feed pressure: Use moderate feed pressure when straight, accurate cutting is desired. Avoid heavy feed pressures because they will cause the power band saw to chatter and vibrate. Study the chips produced. Fine powdery chips indicate the feed is too light. The teeth on the blade are rubbing over the surface of the work instead of cutting the work. Discolored, blued, or straw-colored chips indicate that there is too much feed pressure. This excess pressure can cause teeth to chip and break. In addition, the blade will wear prematurely because of overheating. A free-cut curl indicates ideal feed pressure with the fastest time and the longest blade life. Table 1-2 Common Band Sawing Problems and Their Connections Problem Cause Correction Blade develops Roller guides not correctly Readjust. camber. adjusted. Feeding pressure is too Use lighter feed. heavy. Saw guides too far apart. Adjust closer to work. Blade riding against flange Tilt wheel for proper on metal wheel. blade position. Blade develops Saw is binding in cut. Decrease feeding twist. pressure. Side inserts or rollers of Readjust. saw guides too close to saw. Wrong width of blade for Check for correct radius being cut. blade width.

13 PQ G-P01[ ].qxd 1/24/04 9:10 AM Page 13 Quark03 Quark03:Desktop Folder:REPRO-mille Power Hacksaws, Power Band Saws, and Circular Saws 13 Table 1-2 (continued) Problem Cause Correction Saw dulls Saw speed too great; teeth Reduce saw speed. prematurely. sliding over work instead of cutting. Improper coolant or coolant Check type and improperly directed. mixture of coolant. Apply at the point of cut, saturating teeth evenly. Saw idling through cut. Keep teeth engaged; use positive feeding pressure. Feed too light; teeth sliding Use a feed heavy over work. enough to generate a full curled chip. Saw loses set Saw is too wide for radius Check for the proper prematurely. being cut. width. Saw speed is too fast. Reduce speed. Saw rubbing against vise or Check blade along running deep in guides. complete travel. Saw vibrates Wrong speed for the material Check for the proper in cut. and work thickness. width. Insufficient blade tension. Increase tension. Pitch too coarse. Select a finer pitch. Excessive feeding pressure. Reduce pressure. Saw teeth Pitch too coarse. Use a finer pitch on rip out. thin work sections. Work not tightly clamped Reclamp or hold or held. more firmly to prevent vibration. Sawing dry. Use coolant when possible. Gullets loading. Use a coarser pitch and/or a higher viscosity lubricant or brush to remove chips. Excessive feed pressures. Reduce. (continued)

14 PQ G-P01[ ].qxd 1/24/04 9:10 AM Page 14 Quark03 Quark03:Desktop Folder:REPRO-mille 14 Chapter 1 Table 1-2 (continued) Problem Cause Correction Saw breaks Blade too thick for the Check prematurely. diameter of wheels. recommendations for your machine. Cracking at the weld. Weld improperly made; try a longer annealing period. Pitch is too coarse. Use finer pitch. Excessive feeding pressure or Reduce. blade tension. Guides too tight. Readjust. Courtesy Henry G. Thompson Co., Subsidiary of Vermont American Corporation. One of the most important factors in successful band sawing is a proper cutting speed. If the machine is operated at too fast a speed for the material being cut, the teeth are not allowed sufficient time to dig into the material. As a result, they merely rub over the surface of the work, creating friction that rapidly dulls the cutting edge and wears out the blade. Table 1-3 gives average speeds and cutting rates for cutting a wide variety of commonly used ferrous and nonferrous metals and nonmetallics. These recommendations will ensure optimum performance under most conditions. Table 1-3 Average Speeds and Cutting Rates Flexible and Hard-Back Carbon Raker Tooth Size of Material 1 4 in. 1 2 in. 2 in. 4 in. Material Speed Teeth Speed Teeth Speed Teeth Speed Teeth Steels: Armor plate Angle iron Carbon steels Chromium steels Cold-rolled steel Drill rod Graphite steels High-speed steels

15 PQ G-P01[ ].qxd 1/24/04 9:10 AM Page 15 Quark03 Quark03:Desktop Folder:REPRO-mille Power Hacksaws, Power Band Saws, and Circular Saws 15 Table 1-3 (continued) Flexible and Hard-Back Carbon Raker Tooth Size of Material 1 4 in. 1 2 in. 2 in. 4 in. Material Speed Teeth Speed Teeth Speed Teeth Speed Teeth Machinery steels Molybdenum steels Nickel steels Silicon manganese Stainless steels Structural steels Tungsten steels Foundry metals: Brass hard Brass soft Bronze aluminum Bronze manganese Bronze navel Bronze phosphorous Cast iron gray Cast iron malleable Cast steel Copper beryllium Copper drawn Gunnite Meehanite Monel Nickel cold-rolled Nickel silver Silver (continued)

16 PQ G-P01[ ].qxd 1/24/04 9:10 AM Page 16 Quark03 Quark03:Desktop Folder:REPRO-mille 16 Chapter 1 Table 1-3 (continued) Flexible and Hard-Back Carbon Hook Tooth Size of Material 1 2 in. 2 in. 5 in. 10 in. Material Speed Teeth Speed Teeth Speed Teeth Speed Teeth Nonferrous metals: Aluminum soft Aluminum medium Aluminum hard Babbit Beryllium copper Brass casting Brass commercial Brass naval Brass yellow Cadmium Kirsite Copper Lead Magnesium Silicon bronze Titanium #150A Steels: Alloy steels Low-carbon steel Medium carbon steel High-carbon steel Courtesy Armstrong-Blum Mfg. Co.

17 PQ G-P01[ ].qxd 1/24/04 9:10 AM Page 17 Quark03 Quark03:Desktop Folder:REPRO-mille Power Hacksaws, Power Band Saws, and Circular Saws 17 Friction cutting differs from all other types of metal-sawing methods. It is not actually a cutting operation, but a burning process similar to torch cutting. It is much faster than conventional sawing methods. Very hard materials (which could not normally be sawed) are cut rapidly and easily. Bulky and irregular shapes can be cut handily because there is little blade drag. Basically, the friction-cutting operation involves the use of a very fast moving blade that travels at speeds between 6000 and 18,000 feet per minute (see Table 1-4). At these speeds, terrific heat is built up in the workpiece at its point of contact with the blade, and burning begins. Teeth are not needed to generate burning heat, but they generate increased cutting speed and efficiency by carrying additional oxygen into the work area, thus creating greater oxidation. Set teeth are also important. They give the operator the control required to cut a straight line or follow a specific curve. Table 1-4 Description Recommended Friction Cutting Speeds for Common Metals Armor plate ,000 Carbon steel ,000 Cast steel ,000 Chromium steel ,000 Chromium-vanadium steel ,000 Free-machining steel ,000 Gray cast iron ,000 Malleable cast iron ,000 Manganese steel ,000 Moly steel ,000 Molybdenum ,000 Nickel-chromium steel ,000 Nickel steel ,000 Silicon steel ,000 Stainless steel ,000 Tungsten steel ,000 Average Recommended Cutting Speeds, ft/min. Courtesy Henry G. Thompson Co., Subsidiary of Vermont American Corporation.

18 PQ G-P01[ ].qxd 1/24/04 9:10 AM Page 18 Quark03 Quark03:Desktop Folder:REPRO-mille 18 Chapter 1 There is a definite advantage to using a special blade for this type of operation. The friction-cutting blade is made from special steel. The blade is specially heat-treated to withstand the fast speeds and severe flexing that are encountered in friction sawing. Many difficult manufacturing problems have been solved with friction sawing because this process has distinct advantages. Before deciding whether to use friction sawing, consideration should be given to the specific job requirements. There are important limitations involved with friction sawing. Following are some of these limitations: Friction cutting leaves a very heavy burr on the underside of the material being cut. Thicknesses over 5 8 inch are extremely difficult to cut. Heat from the friction-sawing process may have a tempering effect on the edges of some materials. Circular Saws Circular saws have some advantages. They produce a burr-free mill finish when slow-speed cold sawing is used. This eliminates secondary operations on tubing, channels, angles, and solid stock of most steels and other ferrous materials, as well as most nonferrous metals. The rigidity of the blade produces cuts of extreme accuracy and close tolerances. The cutting operation is safe, clean, and quiet because of the slower speed. Figure 1-8 shows a manually operated saw. Semiautomatic types with an air-operated vise are available. Special vise insets for holding thin-walled pipe or tubing to prevent distortion are shown in Figure 1-9A. The other holding arrangement is shown in Figure 1-9B. This shows square material being held for optimum cutting angle. Other special shapes can be made to fit in the vises, or they can be purchased from the saw manufacturer. The semiautomatic machines have heavy-duty feed mechanisms to feed the metal to the saw. The saw can do straight cutting, miter cutting, slot (or longitudinal) cutting, or any number of other arrangements that will fit within the limits of the machine. Nonferrous Saw A machine specifically suited for aluminum or nonferrous and hard plastics is shown in Figure The machine cuts from the bottom up. The cutting blade speed is 9840 surface feet per minute (sfpm). The workpiece is held from the top by a quick-clamping vise. Maximum saw diameter is 12 inches. A built-in spray mist coolant system provides effective blade lubrication. Mitering is possible in either 45 or 60 and in both directions.

19 PQ G-P01[ ].qxd 1/24/04 9:10 AM Page 19 Quark03 Quark03:Desktop Folder:REPRO-mille Power Hacksaws, Power Band Saws, and Circular Saws 19 Figure 1-8 Manually operated metal-cutting table saws. (Courtesy of Kalamazoo Saw from Clausing Industrial Inc.) Figure 1-9 Special vise inserts. (Courtesy of Kalamazoo Saw from Clausing Industrial Inc.) Blade The circular saw blade is the most important part of the saw. It is chosen to do a specific job. The blade is important for the quality of the cut. High-speed blades are coated with a special nitrate treatment to retain strength and hardness, as well as to facilitate coolant penetration. Carbide-tipped blades are made of a special alloy with carbide-tipped teeth for high-speed cutting of aluminum and other light nonferrous materials.

20 PQ G-P01[ ].qxd 1/24/04 9:10 AM Page 20 Quark03 Quark03:Desktop Folder:REPRO-mille 20 Chapter 1 Figure 1-10 High-speed aluminum and nonferrous saw. (Courtesy of Kalamazoo Saw from Clausing Industrial Inc.) Table 1-5 shows the approximate number of teeth for the blade diameter. This table indicates the actual number of teeth engaged with the material being cut. No fewer than two to three teeth should engage the work at all times. No more than seven teeth should be engaging the work at any one time. Table 1-6 shows the blade pitch and the number of teeth per inch. Table 1-7 indicates the blade speed in feet per minute for the different spindle speeds and blade diameters. Table 1-8 shows recommended sawing speeds for various materials cut by this type of saw. Table 1-9 indicates the spindle speeds available for five different models of saws. The spindle speeds for the circular saws for ferrous metals are 26 to 52 rpm, or a very slow speed. The nonferrous model saw uses a speed of 3000 rpm, or a somewhat faster saw blade. Table 1-5 Approximate Number of TPI Number of Teeth on Blade Blade Diameter, in

21 PQ G-P01[ ].qxd 1/24/04 9:10 AM Page 21 Quark03 Quark03:Desktop Folder:REPRO-mille Power Hacksaws, Power Band Saws, and Circular Saws 21 Table 1-5 (continued) Number of Teeth on Blade Blade Diameter, in Courtesy Startrite, Inc. Table 1-6 Pitch Selection Pitch Designation Approx. Teeth per Inch Table 1-7 Blade Speeds (fpm) Blade Diameter, in. Spindle Speed, rpm Material Table 1-8 Recommended Sawing Guide Blade Speed, ft/min. Mild steel High-carbon, stainless, alloys, tool steel Cast iron Bronze Brass, copper Aluminum

22 PQ G-P01[ ].qxd 1/24/04 9:10 AM Page 22 Quark03 Quark03:Desktop Folder:REPRO-mille 22 Chapter 1 Model Table 1-9 Startrite Spindle Speeds CF CF CF CF CN 300 T 300 Spindle Speed, rpm Courtesy Startrite Corp. Summary Power hacksaws, power band saws, and circular saws are very important to machine shop operations. A large number of power hacksaws are in use in the metalworking industry. A power hacksaw is an essential machine in most machine shop operations. It is designed to make the sawing of metal a mechanical operation. High-speed tungsten steel and high-speed molybdenum steel are the most commonly used materials in power saw blades. High-speed, shatterproof blades are designed to meet safety and performance requirements. These blades are designed with 12-inch, 14-inch, and 17-inch lengths with a 1-inch or inch width. In the past few years, the power band saw has become very important in machine shop operations. In some instances it is used in production operations prior to final machining operations. There are three types of saw blades: the regular tooth, skip tooth, and hook tooth. Small and thin-wall sections of metal require a finetooth blade. Large metal sections require the use of blades with coarse teeth so that adequate chip clearance is provided. Two teeth should be engaged in the metal to be cut at all times. Soft, easily machined materials require slightly coarser teeth to provide chip clearance. Hard metals of low machinability require finer teeth so that there are more cutting edges per inch. Stainless steel should be sawed with a coarse-tooth saw blade for best results. Cast iron is always cut dry. Almost all the commercially available soluble oils or light cutting oils will give good results when cutting ferrous metals. When aluminum is cut, paraffin and beeswax are commonly used lubricants. Cutting oil mineral base with fatty oils added is one of four types of cutting fluids. Cutting oil with light viscosity fatty oils is another, as well as synthetic water-soluble cutting agent and soluble oil cutting agent with fatty oils and sulfurized for extreme pressure with antiweldment properties.

23 PQ G-P01[ ].qxd 1/24/04 9:10 AM Page 23 Quark03 Quark03:Desktop Folder:REPRO-mille Power Hacksaws, Power Band Saws, and Circular Saws 23 The three types of feeds used on power band saws are hand, hydraulic, and mechanical. Many difficult manufacturing problems have been solved with friction sawing. This process has distinct advantages. Some of the limitations are important. Friction cutting leaves a very heavy burr on the underside of the material being cut, thicknesses over 5 8 inch are extremely difficult to cut, and heat from the friction-sawing process may have a tempering effect on the edges of some materials. Circular saws have some advantages. They produce a burr-free mill finish when slow-speed cold sawing is used. This eliminates secondary operations on tubing, channels, angles, and solid stock. The rigidity of the blade produces cuts of extreme accuracy and close tolerances. Review Questions 1. Why are power hacksaws preferred in the machine shop? 2. Brass may be cut at the same speed as if a suitable cutting compound is used. 3. List the basic parts of a power hacksaw. 4. What are the three basic types of tooth set on metal-cutting band saw blades? 5. A 1-inch band saw blade can cut with a radius of inches. 6. Why is soluble oil cutting agent water-soluble? 7. Does cast iron need a cutting fluid? Why? 8. What is the probable cause when the blade develops a twist? 9. What is the recommended correction for a twisted blade problem? 10. What are the recommended friction-cutting speeds for gray cast iron? 11. What are three of the limitations to friction cutting? 12. What are the advantages of using circular saws for cutting? 13. How many teeth per inch (TPI) are actually cutting the metal with a 14-inch, 100-tooth blade? 14. Why do some power hacksaws need a coolant system? 15. What type of blades do power hacksaws use?

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